Spheroidal polymerization catalyst, process for preparing, and use for ethylene polymerization

ABSTRACT

A catalyst composition formed from selected organoaluminum compounds and a precursor composition of the formula 
     
         Mg.sub.m Ti.sub.l (OR).sub.n X.sub.p [ED].sub.q [Filler].sub.r 
    
     wherein ED is a selected electron donor compound 
     R is a C 1  to C 14 , aliphatic or aromatic hydrocarbon radical, or COR&#39; wherein R&#39; is a C 1  to C 14  aliphatic or aromatic hydrocarbon radical, X is Cl, Br, I, or mixtures thereof, Filler is an inert organic or inorganic compound, and, based on the total weight of such composition 
     m is ≧0.5 to ≦56 
     n is 0 or 1 
     p is ≧6 to ≦116 
     q is ≧2 to ≦85 
     r has a value such that the percent filler is from about 10 to about 95 weight percent based on the total weight of the precursor composition. 
     A process for preparing such precursor composition by spray drying it from a slurry or solution in said electron donor compound, using atomization. 
     A process for using said catalyst to readily prepare ethylene polymers having a density of about ≧0.91 to ≦0.97, a melt flow ratio of ≧22 to ≦32 and a bulk density of about 18 to 32 lbs/ft 3  and controlled particle shape and size in a low pressure gas phase process at a productivity of ≧50,000 pounds of polymer per pound of Ti.

CROSS-REFERENCES TO RELATED PATENT APPLICATIONS

This application is a division of our prior U.S. application Ser. No.95,010, filed Nov. 28, 1979, now U.S. Pat. No. 4,293,673, which is acontinuation-in-part of application Ser. No. 974,013, filed Dec. 28,1978, now abandoned.

BACKGROUND OF THE INVENTION

The invention relates to the catalytic polymerization of ethylene withparticularly produced high activity Mg and Ti containing complexcatalysts in a low pressure gas phase process to produce polymers havinga density of ≧0.91 to ≦0.97, a melt flow ratio of ≧22 to ≦32, a bulkdensity of 18 to 32 lbs/ft³ and controlled particle shape and size.

DESCRIPTION OF THE PRIOR ART

To be commercially useful in a gas phase process, such as the fluid bedprocess of U.S. Pat. Nos. 3,709,853; 4,003,712 and 4,011,382, andCanadian Pat. No. 991,798 and Belgian Pat. No. 839,380, the catalystemployed must be a high activity catalyst, that is, it must have a levelof productivity of ≧50,000, and preferably of ≧100,000, pounds ofpolymer per pound of primary metal in the catalyst. This is so becausesuch gas phase processes usually do not employ any catalyst residueremoving procedures. Thus, the catalyst residue in the polymer must beso small that it can be left in the polymer without causing any undueproblems in the hands of the resin fabricator and/or ultimate consumer.Where a high activity catalyst is successfully used in such fluid bedprocesses the heavy metal content of the resin is of the order of ≦20parts per million (ppm) of primary metal at a productivity level of≧50,000. Low catalyst residue contents are also important where thecatalyst is made with chlorine containing materials such as thetitanium, magnesium and/or aluminum chlorides used in some so-calledZiegler or Ziegler-Natta catalysts. High residual chlorine values in amolding resin will cause pitting and corrosion on the metal surfaces ofthe molding devices. Molding grade resins having Cl residues of theorder of ≧200 ppm are not commercially useful.

U.S. Pat. Nos. 3,922,322 and 4,035,560 disclose the use of several Tiand Mg containing catalysts for the manufacture of granular ethylenepolymer in a gas phase fluid bed process under a pressure of <1000 psi.The use of these catalysts in these processes, however, have significantdisadvantages. The catalysts of U.S. Pat. No. 3,922,322 provide polymershaving a very high catalyst residue content, i.e., about 100 ppm of Tiand greater than about 300 ppm Cl, according to the working example ofthis patent. Further, as disclosed in the working example of U.S. Pat.No. 3,922,322, the catalyst is used in the form of a prepolymer, andvery high volumes of the catalyst composition must be fed to the reactorrelative to the volume of polymer made in the reactor. The preparationand use of this catalyst thus requires the use of relatively large sizedequipment for the manufacture, storage and transporting of the catalyst.

The catalysts of U.S. Pat. No. 4,035,560 also apparently providepolymers having high catalyst residues, and the catalyst compositionsare apparently pyrophoric because of the types and amounts of reducingagents employed in such catalysts.

U.S. Pat. No. 3,953,414, issued Apr. 27, 1976, describes thepolymerization of olefins with a catalyst prepared from a supportedcatalyst forming component and wherein the polymers are in the form ofparticles which have the shape of the supported component which isspherical or spheroidal. The catalysts are prepared by mixing (a)catalyst-forming components of organometallic compounds of metalsbelonging to Groups II or III of the Periodic Table with (b) supportedcomponents which are products consisting of a carrier comprising ananhydrous Mg halide and halogenated Ti compounds chemically combinedwith, or dispersed on, the carrier. The (b) components are in the formof spherical or spheroidal particles of a size between 1 and 350microns. The (b) component of the catalyst is prepared in differentways, one of which consists of spraying solutions of an anhydrous Mgdihalide in an organic solvent. The spraying is conducted so as to yieldspherically shaped particles which are between 1 and 300 microns insize. The removal of the solvent combined with the carrier is completedby heating the particles under reduced pressure. The particles of thecarrier are then contacted with a halogenated Ti compound. The examplesin the patent disclose the use of the catalysts in a slurrypolymerization process.

U.S. Pat. No. 4,111,835, which issued Sept. 5, 1978, describes thepolymerization of olefins to produce spheroidially shaped resinparticles which are highly resistant to crumbling when thepolymerization is carried out on a continuous scale. The catalyst isformed from (a) an organometallic compound of a metal of Group II or IIIof the Periodic Table and (b) a product obtained by reacting ahalogenated titanium compound with a Mg hydrate halide in the form ofspheroidal particles having particle sizes between 10 and 70 microns.The Mg hydrate halide contains from 10 to 45 percent by weight of waterand is obtained by partial dehydration of a Mg hydrate halide preparedby direct synthesis from electrolytic Mg and hydrochloric acid followedby fractional crystallization of the synthesis product. The Mg hydratehalide is spray dried to obtain spherical particles. The Mg hydratehalide used as the support may be used in admixture with 20-80% byweight of cocarriers which are inert towards the Mg halide and which arecompounds belonging to Groups I to IV of the Periodic Table. Theexamples in the patent describe the use of the catalysts in a slurrypolymerization process.

Thus, U.S. Pat. Nos. 3,953,414 and 4,111,835 describe the preparation ofethylene polymers, exemplified by a slurry polymerization process, usingparticularly prepared catalyst components wherein a component of thecatalyst (catalyst support) is spray dried to form spheroidal particles.

Further, the process of these patents is carried out using largeconcentrations of boiling TiCl₄ which is highly corrosive. Also, complexmulti-step processes are involved. Moreover, the patents describe theuse of hydrates which contain water. This water can be detrimental tothe effectiveness of the catalyst.

U.S. patent application Ser. No. 892,325, filed Mar. 31, 1978, andrefiled as Ser. No. 014,414 on Feb. 27, 1979, in the names of F. J.Karol et al., and entitled Preparation of Ethylene Copolymers in FluidBed Reactor, now U.S. Pat. No. 4,302,566, discloses that ethylenecopolymers, having a density of 0.91 to 0.96, a melt flow ratio of ≧22to ≦32 and a relatively low residual catalyst content can be produced ingranular form, at relatively high productivities, if the monomer(s) arepolymerized in a gas phase process with a specific high activity Mg-Ticontaining complex catalyst which is blended with an inert carriermaterial. The granular polymers thus produced have excellent physicalproperties which allow them to be used in a broad range of moldingapplications.

U.S. patent application Ser. No. 892,037 filed on Mar. 31, 1978, andrefiled as Ser. No. 014,412 on Feb. 27, 1979, in the names of B. E.Wagner et al. and entitled Polymerization Catalyst, Process forPreparing, And Use For Ethylene Homopolymerization, discloses thatethylene homopolymers having a density range of 0.958 to 0.972 and amelt flow ratio of ≧22 to ≦32 and which have a relatively low residualcatalyst residue can be produced at relatively high productivities forcommercial purposes by a low pressure gas phase process if the ethyleneis homopolymerized in the presence of a high activity magnesium-titaniumcomplex catalyst blended with an inert carrier material.

The above noted U.S. patent application Ser. Nos. 892,325; 892,037;014,414 and 014,412 are hereinafter referred to as The Prior U.S.Applications.

However, the polymers produced with the blended catalysts of The PriorU.S. Applications have the disadvantage in that the polymer particlesformed during the fluid bed polymerization process are irregular inshape and are somewhat difficult to fluidize. Also, the final productcontains a relatively high level of fines, i.e., particles having aparticle size of ≦125 microns.

Further, the method employed to form the catalyst precursor compositionas described in The Prior U.S. Applications involves forming theprecursor by dissolving a titanium compound and magnesium compound in anelectron donor compound. The precursor composition is then generallyisolated by crystallization or by precipitation with a C₅ to C₈aliphatic or aromatic hydrocarbon. However, these isolation techniquescan lead to nonuniform polymer particle growth and needle shaped polymerproducts.

U.S. patent application Ser. No. 892,322 filed on Mar. 31, 1978, andrefiled as Ser. No. 012,720 on Feb. 16, 1979, in the names of G. L.Goeke et al. and entitled Impregnated Polymerization Catalyst, ProcessFor Preparing, And Use For Ethylene Copolymerization, now U.S. Pat. No.4,302,565, discloses that ethylene copolymers having a density of about0.91 to 0.94 and a melt flow ratio of ≧22 to ≦32 and which have arelatively high bulk density and which provide films of good clarity canbe produced at relatively high productivities for commercial purposes bya gas phase process if the ethylene is copolymerized with one or more C₃to C₈ alpha olefins in the presence of a high activitymagnesium-titanium complex catalyst prepared under specific activationconditions with an organoaluminum compound and impregnated in a porousinert carrier material.

However, the preparation of the impregnated catalyst precursor as taughtin Ser. Nos. 892,322/012,720 can be difficult to control and the carriermaterial used for the impregnation can be of variable composition. Ifconsiderable care is not taken, variable catalyst performance can occur.Since polymer morphology appears to be dependent on the morphology ofthe carrier used for the catalyst, total flexibility and control ofpolymer particle characteristics is, at times, not possible.

SUMMARY OF THE INVENTION

It has now been unexpectedly found that ethylene polymers having a widedensity range of about ≧0.91 to ≦0.97, a bulk density of about 18 to 32lbs/ft³, a melt flow ratio of ≧>to ≦32, and which are of controlledparticle shape and size, and which have a relatively low residualtitanium content can be produced at relatively high productivities forcommercial purposes by a gas phase process if the ethylene ishomopolymerized, or copolymerized with one or more C₃ to C₈ alphaolefins, in the presence of a high activity magnesium-titanium complexcatalyst prepared, as described below, by spray drying amagnesium-titanium containing precursor composition from a slurry orsolution in an electron donor compound and activating such spray driedprecursor composition under specific activation conditions with anorganoaluminum compound.

A further object of this invention is to provide a process for producingethylene polymers of a controlled particle size and shape by controllingthe catalyst size and shape.

Another object of the present invention is to provide granular ethylenepolymers which have a controlled particle size and shape and, as such,are more conducive to being fluidized in a fluid bed process, andwherein the final polymer product contains a relatively low level ofvery small particles, i.e., particles of about <74 microns.

Another object of the present invention is to provide a method ofpreparing a magnesium-titanium containing catalyst precursor compositionof consistent particle shape and size.

Another object of this invention is to provide a simplified method ofpreparing a magnesium-titanium containing catalyst precursorcomposition.

Another object of this invention is to provide a spherical shaped freeflowing catalyst precursor composition.

BRIEF DESCRIPTION OF THE DRAWING

The drawing shows a gas phase fluid bed reactor system in which thecatalyst system of the present invention may be employed.

DESCRIPTION OF THE PREFERRED EMBODIMENT

It has now been found that the desired ethylene polymers having a lowmelt flow ratio, a wide range of density values and relatively high bulkdensity values and controlled particle shape and size can be readilyproduced with relatively high productivities in a low pressure gas phasereaction process if the monomer charge is polymerized or copolymerizedin the presence of a specific high activity catalyst composition whichis prepared from a spray dried precursor composition under a specificset of conditions, as is also detailed below. It has also been foundthat inclusion of inert fillers in the precursor composition improvespolymer morphology.

The Ethylene Polymers

The ethylene polymers have a melt flow ratio of ≧22 to ≦32, andpreferably of ≧25 to ≦30. The melt flow ratio value is another means ofindicating the molecular weight distribution of a polymer. The melt flowratio (MFR) range of ≧22 to ≦32 thus corresponds to a Mw/Mn value rangeof about 2.7 to 4.1 and the MFR range of 24 25 to ≦30 corresponds to aMw/Mn range of about 2.8 to 3.6.

The homopolymers have a density of about ≧0.958 to ≦0.972. Thecopolymers have a density of about ≧0.91 to ≦0.96. The density of thecopolymer, at a given melt index level for the copolymer, is primarilyregulated by the amount of the C₃ to C₈ comonomer which is copolymerizedwith the ethylene. In the absence of the comonomer, the ethylene wouldhomopolymerize with the catalyst of the present invention to providehomopolymers having a density of about ≧0.958. Thus, the addition ofprogressively larger amounts of the comonomers to the copolymers resultsin a progressive lowering of the density of the copolymer. The amount ofeach of the various C₃ to C₈ comonomers needed to achieve the sameresult will vary from monomer to monomer, under the same reactionconditions.

Thus, to achieve the same results, in the copolymers, in terms of agiven density, at a given melt index level, larger molar amounts of thedifferent comonomers would be needed in the order of C₃ >C₄ >C₅ >C₆ >C₇>C₈.

The melt index of a copolymer is a reflection of its molecular weight.Polymers having a relatively high molecular weight, have a relativelylow melt index. Ultra-high molecular weight ethylene polymers have ahigh load (HLMI) melt index of about 0.0 and very high molecular weightethylene polymers have a high load melt index (HLMI) of about 0.0 toabout 1.0. Such high molecular weight polymers are difficult, if notimpossible, to mold in conventional injection molding equipment. Thepolymers made in the process of the present invention, on the otherhand, can be readily molded, in such equipment. They have a standard ornormal load melt index of 24 0.0 to about 100, and preferably of about0.5 to 80, and a high load melt index (HLMI) of about 11 to about 2000.The melt index of the polymers which are made in the process of thepresent invention is a function of a combination of the polymerizationtemperature of the reaction, the density of the copolymer and thehydrogen/monomer ratio in the reaction system. Thus, the melt index israised by increasing the polymerization temperature and/or by decreasingthe density of the polymer and/or by increasing the hydrogen/monomerratio. In addition to hydrogen, other chain transfer agents such asdialkyl zinc compounds may also be used to further increase the meltindex of the copolymers.

The copolymers which may be prepared in the process of the presentinvention are copolymers of a major mol percent (≧90%) of ethylene, anda minor mol percent (≦10%) of one or more C₃ to C₈ alpha olefins. The C₃to C₈ alpha olefins should not contain any branching on any of theircarbon atoms which is closer than the fourth carbon atoms. The preferredC₃ to C₈ alpha olefins are propylene, butene-1, pentene-1, hexene-1,4-methylpentene-1 and octene-1.

The ethylene polymers of the present invention have an unsaturated groupcontent of ≦1, and usually ≧0.1 to ≦0.3, C═C/1000 carbon atoms, and ann-hexane extractables content of less than about 3, and preferably lessthan about 2, weight percent.

The ethylene polymers of the present invention have a residual catalystcontent, in terms of parts per million of titanium metal, of the orderof ≦20 parts per million, (ppm) at a productivity level of ≧50,000, andof the order of ≦10 parts per million at a productivity level of≧100,000, and of the order of ≦5 parts per million at a productivitylevel of ≧200,000.

The ethylene polymers of the present invention have a bulk density ofabout 18 to 32 lbs/ft³. The ethylene polymers are spherical and have anaverage particle size of the order of about 250 to 2550 microns, andpreferably of about 250 to 1525 microns, in diameter.

The homopolymers produced herein are useful for a variety of moldedarticles.

The copolymers of the present invention are useful for making film aswell as being useful in other molding applications.

HIGH ACTIVITY CATALYST

The compounds used to form the high activity catalyst used in thepresent invention comprise at least one titanium compound, at least onemagnesium compound, at least one electron donor compound, at least oneactivator compound, as defined below.

The titanium compound has the structure

    Ti(OR).sub.a X.sub.b

wherein R is a C₁ to C₁₄ aliphatic or aromatic hydrocarbon radical, orCOR' where R' is a C₁ to C₁₄ aliphatic or aromatic hydrocarbon radical,

X is Cl, Br, I or mixtures thereof, a is 0, 1 or 2, b is 1 to 4inclusive and a+b=3 or 4.

The titanium compounds can be used individually or in combinationsthereof, and would include TiCl₃, TiCl₄, Ti(OCH₃)Cl₃, Ti(OC₆ H₅)Cl₃,Ti(OCOCH₃)Cl₃ and Ti(OCOC₆ H₅)Cl₃.

The magnesium compound has the structure:

    MgX.sub.2

wherein X is Cl, Br or I. Such magnesium compounds can be usedindividually or in combinations thereof and would include MgCl₂, MgBr₂and MgI₂. Anhydrous MgCl₂ is the particularly preferred magnesiumcompound.

About 0.5 to 56, and preferably about 1 to 30, mols of the magnesiumcompound are used per mol of the titanium compound in preparing thecatalysts employed in the present invention.

The titanium and magnesium compounds should be of a physical form andchemical nature such that they will have at least partial solubility inthe electron donor compounds, as described below.

The electron donor compounds would include such compounds as alkylesters of aliphatic and aromatic carboxylic acids, aliphatic ethers,cyclic ethers and aliphatic ketones. Among these electron donorcompounds the preferable ones are alkyl esters of C₁ to C₄ saturatedaliphatic carboxylic acids; alkyl esters of C₇ to C₈ aromatic carboxylicacids; C₂ to C₈, and preferably C₃ to C₄, aliphatic ethers; C₃ to C₄cyclic ethers, and preferably C₄ cyclic mono- or di-ether; C₃ to C₆, andpreferably C₃ to C₄, aliphatic ketones; the most preferred of theseelectron donor compounds would include methyl formate, ethyl acetate,butyl acetate, ethyl ether, hexyl ether, tetrahydrofuran, dioxane,acetone and methyl isobutyl ketone.

The electron donor compounds can be used individually or in combinationsthereof.

About 2 to 85, and preferably about 3 to 45, mols of the electron donorcompound are used per mol of Ti.

The activator compound has the structure

    Al(R").sub.c X'.sub.d H.sub.e

wherein X' is Cl or OR'", R" and R'" are the same or different and areC₁ to C₁₄ saturated hydrocarbon radicals, d is 0 to 1.5, e is 1 or 0 andc+d+e=3.

Such activator compounds can be used individually or in combinationsthereof and would include Al(C₂ H₅)₃, Al(C₂ H₅)₂ Cl, Al(i-C₄ H₉)₃, Al₂(C₂ H₅)₃ Cl₃, Al(i-C₄ H₉)₂ H, Al(C₆ H₁₃)₃, Al(C₂ H₅)₂ H and Al(C₂ H₅)₂(OC₂ H₅).

About 10 to 500, and preferably about 10 to 200, mols of the activatorcompound are used per mol of the titanium compound in activating thecatalyst employed in the present invention.

Catalyst Preparation

The catalyst used in the present invention is prepared by firstpreparing a precursor composition from the titanium compound, themagnesium compound, the electron donor compound and filler and spraydrying these compounds, as described below, into spherically shapedparticles having an average particle size of from about 10 to about 200microns. The spherically shaped particles are then treated withactivator compound as described below.

An initial precursor composition is formed by dissolving the titaniumcompound and an excess of the magnesium compound (1≦Mg/Ti≦56) in theelectron donor compound at a temperature of about 20° C. up to theboiling point of the electron donor compound. The titanium compound canbe added to the electron donor compound before or after the addition ofthe magnesium compound, or concurrent therewith. The total or partialdissolution of the titanium compound and the magnesium compound can befacilitated by stirring, and, in some instances by refluxing, these twocompounds in the electron donor compound.

In a separate vessel inert fillers such as magnesium chloride and/orsilica, for example, are slurried in the electron donor compound at atemperature up to the boiling point of the electron donor compound. Thisslurry or solution can then be added, before or after cooling, to thesolution of the Mg/Ti complex. The final slurry thus formed can beoptionally heated to the boiling point of the electron donor prior tothe spray drying.

The precursor slurry is spray-dried at an inlet nitrogen drying gastemperature which is in the range of greater than the electron donorboiling point up to about 150° C. A further variable controlled in theprocess is the solvent vapour pressure. The volume flow of drying gas iscontrolled so as to be considerably larger than the volumetric flow ofthe slurry/solution. The atomization of the slurry can be accomplishedby an atomizing nozzle or a centrifugal high speed disc atomizer atatomizer pressures of between 1 and 200 psig.

The fillers which are added to the solution prior to spray dryinginclude any organic or inorganic compounds which are inert to thetitanium compound and the final active catalyst, such as silicon dioxidesuch as fumed silica, titanium dioxide, polystyrene, rubber modifiedpolystyrene, magnesium chloride and calcium carbonate. These fillers maybe used individually or in combinations thereof.

The amount of filler which can be present in the precursor compositionis from about 10 to about 95 weight percent based on the total weight ofthe precursor composition. The insoluble fillers have an averageparticle size of the order of about ≦50 microns.

When thus made as disclosed above, the precursor composition has theformula,

    Mg.sub.m Ti.sub.1 (OR).sub.n X.sub.p [ED].sub.q [Filler].sub.r

wherein ED is the electron donor compound, R is a C₁ to C₁₄ aliphatic oraromatic hydrocarbon radical, or COR' wherein R' is a C₁ to C₁₄aliphatic or aromatic hydrocarbon radical, X is Cl, Br, I or mixturesthereof. Filler is the inert filler compound, and, based on the totalweight of such composition,

m is ≧0.5 to ≦56, and preferably ≧1.5 to ≦5.0,

n is 0 or 1,

p is ≧6 to ≦116, and preferably ≧6 to ≦14,

q is ≧2 to ≦85, and preferably ≧4 to ≦11,

r has a value such that the percent filler is from about 10 to about 95weight percent.

Activation of Spray Dried Precursor Composition

In order to be used in the process of the present invention the spraydried precursor composition must be fully or completely activated, thatis, it must be treated with sufficient activator compound to transformthe Ti atoms in the precursor composition to an active state. Theactivation procedures which may be used in this regard are describedbelow.

Procedure A (Total Activation in Reactor)

The spray dried precursor composition may be completely activated in thepolymerization reactor. In this procedure, the activator compound andthe spray dried precursor composition are preferably fed to the reactorthrough separate feed lines. The activator compound may be sprayed intothe reactor in an undiluted form or in the form of a solution thereof ina hydrocarbon solvent such as isopentane, hexane, or mineral oil. Thissolution usually contains about 2 to 30 weight percent of the activatorcompound. The activator compound is added to the reactor in such amountsas to provide therein a total Al/Ti molar ratio of 10 to 500, andpreferably of about 10 to 200. The activator compound added to thereactor reacts with, and activates, the titanium compound in thereactor.

Procedure B (Two-Stage Activation Process)

The activation of the spary dried precursor composition may be conductedin two stages.

In the first stage the precursor composition which has been spray driedis reacted with, and is partially activated by, enough activatorcompound so as to provide a partially activated precursor compositionwhich has an activator compound/Ti molar ratio of about >0 to ≦10:1, andpreferably of about 4 to 8:1. The first of these two stages ofactivation may be conducted outside of the reactor. In order to renderthe partially activated precursor composition active for ethylenepolymerization purposes, activator compound is added to thepolymerization reactor to complete, in the reactor, the activation ofthe precursor composition. The additional activator compound and thepartially activated precursor composition or the unactivated precursorcomposition are preferably fed to the reactor through separate feedlines. The activator compound may be sprayed into the reactor in anundiluted form or in the form of a solution thereof in a hydrocarbonsolvent such as isopentane, hexane, or mineral oil. This solutionusually contains about 2 to 30 weight percent of the activator compound.The activator compound is added to the reactor in such amounts as toprovide, in the reactor, with the amounts of activator compound andtitanium compound fed with the partially activated and spray driedprecursor composition, a total Al/Ti molar ratio of 10 to 500, andpreferably of about 10 to 200. The activator compound added to thereactor, reacts with, and activates or completes the activation of, thetitanium compound in the reactor.

In a continuous gas phase process, such as the fluid bed processdisclosed below, discrete portions of the spray dried precursorcomposition or partially activated precursor composition arecontinuously fed to the reactor with discrete portions of activatorcompound needed to activate or complete the activation of the partiallyactivated precursor composition, during the continuing polymerizationprocess in order to replace active catalyst sites that are expendedduring the course of the reaction.

The Polymerization Reaction

The polymerization reaction is conducted by contacting a stream of themonomer(s), in a gas phase process, such as in the fluid bed processdescribed below, and substantially in the absence of catalyst poisonssuch as moisture, oxygen, CO, CO₂, and acetylene with a catalyticallyeffective amount of the completely activated precursor composition (thecatalyst) at a temperature and at a pressure sufficient to initiate thepolymerization reaction.

In order to achieve the desired density ranges in the copolymers it isnecessary to copolymerize enough of the ≧C₃ comonomers with ethylene toachieve a level of >0 to 10 mol percent of the C₃ to C₈ comonomer in thecopolymer. The amount of comonomer needed to achieve this result willdepend on the particular comonomer(s) employed.

There is provided below a listing of the amounts, in mols, of variouscomonomers that are copolymerized with ethylene in order to providepolymers having the desired density range at any given melt index. Thelisting also indicates the relative molar concentration, of suchcomonomers to ethylene, which are in the recycled gas stream of monomersunder reaction equilibrium conditions in the reactor.

    ______________________________________                                                                 Gas Stream                                                       mol % needed Comonomer/Ethylene                                   Comonomer   in copolymer molar ratio                                          ______________________________________                                        propylene   >0 to 10     >0 to 0.9                                            butene-1    >0 to 7.0    >0 to 0.7                                            pentene-1   >0 to 6.0    >0 to 0.45                                           hexene-1    >0 to 5.0    >0 to 0.4                                            octene-1    >0 to 4.5    >0 to 0.35                                           ______________________________________                                    

A fluidized bed reaction system which can be used in the practice of theprocess of the present invention is illustrated in the drawing. Withreference thereto the reactor 1 consists of a reaction zone 2 and avelocity reduction zone 3.

The reaction zone 2 comprises a bed of growing polymer particles, formedpolymer particles and a minor amount of catalyst particles fluidized bythe continuous flow of polymerizable and modifying gaseous components inthe form of make-up feed and recycle gas through the reaction zone. Tomaintain a viable fluidized bed, the mass gas flow rate through the bedmust be above the minimum flow required for fluidization, and preferablyfrom about 1.5 to about 10 times G_(mf) and more preferably from about 3to about 6 times G_(mf). G_(mf) is used in the accepted form as theabbreviation for the minimum mass gas flow required to achievefluidization, C. Y. Wen and Y. H. Yu, "Mechanics of Fluidization",Chemical Engineering Progress Symposium Series, Vol. 62, p. 100-111(1966).

It is essential that the bed always contains particles to prevent theformation of localized "hot spots" and to entrap and distribute theparticulate catalyst throughout the reaction zone. On start up, thereactor is usually charged with a base of particulate polymer particlesbefore gas flow is initiated. Such particles may be identical in natureto the polymer to be formed or different therefrom. When different, theyare withdrawn with the desired formed polymer particles as the firstproduct. Eventually, a fluidized bed of the desired polymer particlessupplants the start-up bed.

The spray dried precursor composition or the partially activatedprecursor composition used in the fluidized bed is preferably stored forservice in a reservoir 4 under a blanket of a gas which is inert to thestored material, such as nitrogen or argon.

Fluidization is achieved by a high rate of gas recycle to and throughthe bed, typically in the order of about 50 times the rate of feed ofmake-up gas. The fluidized bed has the general appearance of a densemass of viable particles in possible free-vortex flow as created by thepercolation of gas through the bed. The pressure drop through the bed isequal to or slightly greater than the mass of the bed divided by thecross-sectional area. It is thus dependent on the geometry of thereactor

Make-up gas is fed to the bed at a rate equal to the rate at whichparticulate polymer product is withdrawn. The composition of the make-upgas is determined by a gas analyzer 5 positioned above the bed. The gasanalyzer determines the composition of the gas being recycled and thecomposition of the make-up gas is adjusted accordingly to maintain anessentially steady state gaseous composition within the reaction zone.

To insure complete fluidization, the recycle gas and, where desired,part of the make-up gas are returned over gas recycle line 6 to thereactor at point 7 below the bed. There exists a gas distribution plate8 above the point of return to aid fluidizing the bed.

The portion of the gas stream which does not react in the bedconstitutes the recycle gas which is removed from the polymerizationzone, preferably by passing it into a velocity reduction zone 3 abovethe bed where entrained particles are given an opportunity to drop backinto the bed.

The recycle gas is then compressed in a compressor 9 and then passedthrough a heat exchanger 10 wherein it is stripped of heat of reactionbefore it is returned to the bed. The temperature of the bed iscontrolled at an essentially constant temperature under steady stateconditions by constantly removing heat of reaction. No noticeabletemperature gradient appears to exist within the upper portion of thebed. A temperature gradient will exist in the bottom of the bed in alayer of about 6 to 12 inches, between the temperature of the inlet gasand the temperature of the remainder of the bed. The recycle is thenreturned to the reactor at its base 7 and to the fluidized bed throughdistribution plate 8. The compressor 9 can also be placed downstream ofthe heat exchanger 10.

The distribution plate 8 plays an important role in the operation of thereactor. The fluidized bed contains growing and formed particulatepolymer particles as well as catalyst particles. As the polymerparticles are hot and possibly active, they must be prevented fromsettling, for if a quiescent mass is allowed to exist, any activecatalyst contained therein may continue to react and cause fusion.Diffusing recycle gas through the bed at a rate sufficient to maintainfluidization throughout the bed is, therefore, important. Thedistribution plate 8 serves this purpose and may be a screen, slottedplate, perforated plate, a plate of the bubble cap type and the like.The elements of the plate may all be stationary, or the plate may be ofthe mobile type disclosed in U.S. Pat. No. 3,298,792. Whatever itsdesign, it must diffuse the recycle gas through the particles at thebase of the bed to keep the bed in a fluidized condition, and also serveto support a quiescent bed of resin particles when the reactor is not inoperation. The mobile elements of the plate may be used to dislodge anypolymer particles entrapped in or on the plate.

Hydrogen may be used as a chain transfer agent in the polymerizationreaction of the present invention. The ratio of hydrogen/ethyleneemployed will vary between about 0 to about 2.0 moles of hydrogen permole of the monomer in the gas stream.

Any gas inert to the catalyst and reactants can also be present in thegas stream. The activator compound is preferably added to the reactionsystem downstream from heat exchanger 10. Thus, the activator compoundmay be fed into the gas recycle system from dispenser 11 thru line 12.

Compounds of the structure Zn(R_(a))(R_(b)), wherein R_(a) and R_(b) arethe same or different C₁ to C₁₄ aliphatic or aromatic hydrocarbonradicals, may be used in conjunction with hydrogen, with the catalystsof the present invention as molecular weight control or chain transferagents, that is, to increase the melt index values of the copolymersthat are produced. About 0 to 100, and preferably about 20 to 30 molesof the Zn compound (as Zn) would be used in the gas stream in thereactor per mol of titanium compound (as Ti) in the reactor. The zinccompound would be introduced into the reactor, preferably in the form ofa dilute solution (2 to 30 weight percent) in a hydrocarbon solvent orabsorbed on a solid diluent material, such as silica, in amounts ofabout 10 to 50 weight percent. These compositions tend to be pyrophoric.The zinc compound may be added alone, or with any additional portions ofthe activator compound that are to be added to the reactor from afeeder, not shown, which could be positioned adjacent dispenser 11.

It is essential to operate the fluid bed reactor at a temperature belowthe sintering temperature of the polymer particles to insure thatsintering will not occur. For the production of ethylene homopolymersand copolymers in the process of the present invention an operatingtemperture of about 30° to 115° C. is generally employed. Temperaturesof about 75° to 95° C. are used to prepare products having a density ofabout 0.91 to 0.92, and temperatures of about 80° to about 100° C. areused to prepare products having a density of about >0.92 to 0.94, andtemperatures of about 90° to 115° C. are used to prepare products havinga density of about >0.94 to 0.97.

The fluid bed reactor is operated at pressures of up to about 1000 psi,and is preferably operated at a pressure of from about 150 to 350 psi,with operation at the higher pressures in such ranges favoring heattransfer since an increase in pressure increases the unit volume heatcapacity of the gas.

The spray dried precursor or partially activated spray dried precursorcomposition is injected into the bed at a rate equal to its consumptionat a point 13 which is above the distribution plate 8. Preferably, thecatalyst is injected at a point in the bed where good mixing of polymerparticles occurs. Injecting the catalyst at a point above thedistribution plate is an important feature of this invention. Since thecatalysts used in the practice of the invention are highly active,injection of the fully activated catalyst into the area below thedistribution plate may cause polymerization to begin there andeventually cause plugging of the distribution plate. Injection into theviable bed, instead, aids in distributing the catalyst throughout thebed and tends to preclude the formation of localized spots of highcatalyst concentration which may result in the formation of "hot spots".Injection of the catalyst into the reactor above the bed may result inexcessive catalyst carryover into the recycle line where polymerizationmay begin and plugging of the line and heat exchanger may eventuallyoccur.

A gas which is inert to the catalyst such as nitrogen or argon is usedto carry the partially or completely reduced precursor composition, andany additional activator compound or non-gaseous chain transfer agentthat is needed, into the bed.

The production rate of the bed is controlled by the rate of catalystinjection. The production rate may be increased by simply increasing therate of catalyst injection and decreased by reducing the rate ofcatalyst injection.

Since any change in the rate of catalyst injection will change the rateof generation of the heat of reaction, the temperature of the recyclegas entering the reactor is adjusted upwards or downwards to accommodatethe change in rate of heat generation. This insures the maintenance ofan essentially constant temperature in the bed. Complete instrumentationof both the fluidized bed and the recycle gas cooling system is, ofcourse, necessary to detect any temperature change in the bed so as toenable the operator to make a suitable adjustment in the temperature ofthe recycle gas.

Under a given set of operating conditions, the fluidized bed ismaintained at essentially a constant height by withdrawing a portion ofthe bed as product at a rate equal to the rate of formation of theparticulate polymer product. Since the rate of heat generation isdirectly related to product formation, a measurement of the temperaturerise of the gas across the reactor (the difference between inlet gastemperature and exit gas temperature) is determinative of the rate ofparticulate polymer formation at a constant gas velocity.

The particulate polymer product is preferably continuously withdrawn ata point 14 at or close to the distribution plate 8 and in suspensionwith a portion of the gas stream which is bented as the particles settleto minimize further polymerization and sintering when the particlesreach their ultimate collection zone. The suspending gas may also beused to drive the product of one reactor to another reactor.

The particulate polymer product is conveniently and preferably withdrawnthrough the sequential operation of a pair of timed valves 15 and 16defining a segregation zone 17. While valve 16 is closed, valve 15 isopened to emit a plug of gas and product to the zone 17 between it andvalve 15 which is then closed. Valve 16 is then opened to deliver theproduct to an external recovery zone. Valve 16 is then closed to awaitthe next product recovery operation. The vented gas containing unreactedmonomers may be recovered from zone 17 through line 18 and recompressedin compressor 19 and returned directly, or through a purifier 20, overline 21 to gas recycle line 6 at a point upstream of the recyclecompressor 9.

Finally, the fluidized bed reactor is equipped with an adequate ventingsystem to allow venting the bed during start up and shut down. Thereactor does not require the use of stirring means and/or wall scrapingmeans. The recycle gas line 6 and the elements therein (compressor 9,heat exchanger 10) should be smooth surfaced, and devoid of unnecessaryobstructions so as not to impede the flow of recycle gas.

The highly active spray-dried catalyst system of this invention appearsto yield a fluid bed product having an average particle size betweenabout 250 to about 2550, and preferably about 250 to about 1525,microns.

The feed stream of gaseous monomer, with or without inert gaseousdiluents, is fed into the reactor at a space time yield of about 2 to 10pounds/hour/cubic foot of bed volume.

The term virgin resin or polymet as used herein means polymer, ingranular form, as it is recovered from the polymerization reactor.

The following Examples are designed to illustrate the process of thepresent invention and are not intended as a limitation upon the scopethereof.

The properties of the polymers produced in the Examples were determinedby the following test methods:

    ______________________________________                                        Density     For materials having a density of                                             <0.940, ASTM-1505 procedure is used                                           and plaque is conditioned for one                                             hour at 100° C. to approach equilibrium                                crystallinity. For materials having                                           density of ≧0.940 a modified procedure                                 is used wherein the test plaque is                                            conditioned for one hour at 120° C. to                                 approach equilibrium crystallinity                                            and is then quickly cooled to room                                            temperature. All density values                                               are reported as grams/cm.sup.3. All density                                   measurements are made in a density                                            gradient column.                                                  Melt Index (MI)                                                                           ASTM D-1238 - Condition E - Measured                                          at 190° C. - reported as grams per 10                                  minutes.                                                          Flow Rate (HLMI)                                                                          ASTM D-1238 - Condition F - Measured                                          at 10 times the weight used in the                                            melt index test above.                                            Melt Flow Ratio                                                                            ##STR1##                                                         Productivity                                                                              a sample of the resin product is ashed                                        and the weight percent of ash is                                              determined; since the ash is essentially                                      composed of the catalyst, the productivity                                    is thus the pounds of polymer produced                                        per pound of titanium metal consumed.                                         The amount of Ti, Mg and halide in                                            the ash are determined by elemental                                           analysis. The values are reported in                                          parts per million (ppm) of titanium                                           metal.                                                            Bulk density                                                                              The resin is poured via 3/8" diameter                                         funnel into a 100 ml graduated cylinder                                       to 100 ml line without shaking the                                            cylinder, and weighed by difference.                                          The values are reported in lbs/ft.sup.3.                          Average Particle                                                                          This is calculated from sieve analysis                            Size        data measured according to ASTM-D-1921                                        Method A using a 500 g sample.                                                Calculations are based on weight                                              fractions retained on the screens.                                Molecular Weight                                                                          Gel Permeation Chromatography                                     Distribution                                                                              For resins with density <0.94:                                    (Mw/Mn)     Styrogel Packing: (Pore size                                                  Sequence is 10.sup.7, 10.sup.5, 10.sup.4,                                     10.sup.3, 60 A°) Solvent is                                            Perchloroethylene at 117° C.                                           For resins with density ≧0.94:                                         Styrogel Packing: (Pore Size                                                  Sequence is 10.sup.7, 10.sup.6, 10.sup.5, 10.sup.4,                           60 A°) Solvent is ortho dichloro                                       Benzene at 135° C.                                                     Detection for all resins:                                                     Infra red at 3.45μ                                             n-hexane    FDA test used for polyethylene                                    extractables                                                                              Film intended for food contact                                                applications). A 200 square inch                                              sample of 1.5 mil gauge film is                                               cut into strips measuring 1"× 6"                                        and weighed to the nearest 0.1 mg.                                            The strips are placed in a vessel                                             and extracted with 300 ml of n-hexane                                         at 50 ± 1° C. for 2 hours. The                                      extract is then decanted into tared                                           culture dishes. After drying the                                              extract in a vacuum desiccator the                                            culture dish is weighed to the                                                nearest 0.1 mg. The extractables,                                             normalized with respect to the                                                original sample weight, is then                                               reported as the weight fraction                                               of n-hexane extractables.                                         Unsaturation                                                                              Infrared Spectrophotometer (Perkin                                            Elmer Model 21). Pressings made                                               from the resin which are 25 mils                                              in thickness are used as test                                                 specimens. Absorbance is measured                                             at 10.35μ for transvinylidene                                              unsaturation, 11.0μ for terminal                                           vinyl unsaturation, and 11.25μ                                             for pendant vinylidene unsaturation.                                          The absorbance per mil of thickness                                           of the pressing is directly                                                   proportional to the product of                                                unsaturation concentration and                                                absorbtivity. Absorbtivities are                                              taken from the literature values                                              of R. J. de Kock, et al, J. Polymer                                           Science, Part B, 2, 339, (1964).                                  ______________________________________                                    

I. Preparation of Spray Dried Precursor

In a 5 liter flask equipped with a mechanical stirrer was placed 1.0liter of tetrahydrofuran (THF). 71.0 g of anhydrous magnesium chloridewas slowly added to the THF while stirring under a nitrogen atmosphere.The temperature of this exothermic reaction was controlled by the rateof addition of the magnesium chloride and by using a water bath. Whenthe addition of the magnesium chloride was complete, 90.0 g of fumedsilica was slowly added to the slurry. Upon the completion of theaddition of the fumed silica the slurry was refluxed for a period of 2to 6 hours. (The fumed silica had a particle size in the range of 0.007to 0.05 microns and is sold commercially as CAB-O-SIL fumed silica byCabot Corporation. It has an SiO₂ content of <99.8%).

In a separate 2 liter flask equipped with a mechanical stirrer 13.4 g ofanhydrous MgCl₂ was mixed with 0.8 liter of THF under nitrogen. Themixture was stirred at room temperature (˜25° C.) while 8.9 ml of TiCl₄was added dropwise over a 1/2 hour period. After complete addition ofthe TiCl₄, the contents of the flask were heated to reflux for about 1/2to 1 hour to dissolve the solids. The system was cooled to roomtemperature under agitation. The contents of this flask were then slowlyadded to the contents of the slurry of magnesium chloride previouslyprepared. The contents of the vessel were refluxed with stirring forabout 1 hour and then cooled to room temperature with stirring. Thefinal product was a yellowish-green colored slurry which remained insuspension for about 1 hour before separating.

The slurry/suspension was spray dried in an inert atmosphere with aspray-drier having two nozzles having a diameter of 0.06 inches and anannular ring diameter of 0.10 inches under an atomization pressure of 10psi and at a drying nitrogen inlet gas temperature of 112° C. Thespherically shaped catalyst particles collected in a cyclone had anaverage particle diameter of about 25 microns as measured from opticalmicrographs.

II. Activation Procedure

The precursor compositions as formed in I above were activated bydifferent procedures.

Procedure A (Total Activation in Reactor)

The activator compound is fed to the polymerization reactor for thepurpose of activating the precursor composition. It is fed into thereactor as a dilute solution in a hydrocarbon solvent such asisopentane. These dilute solutions contain about 2 to 30% by weight ofthe activator compound.

The activator compound is added to the polymerization reactor so as tomaintain the Al/Ti ratio in the reactor at a level of about 10 to 500and preferably of 10 to 200.

Procedure B (Two-Stage Activation Process)

The precursor composition as formed in I above was activated by addingsaid precursor composition and activator compound to a mixing tank withsufficient amounts of anhydrous aliphatic hydrocarbon diluent such asisopentane to provide a slurry system.

The activator compound and precursor compound are used in such amountsas to provide a partially activated precursor composition which has anAl/Ti ratio of >0 to ≦10:1 and preferably of 4 to 8:1.

The contents of the slurry system are then thoroughly mixed at roomtemperature and at atmospheric pressure for about 1/4 to 1/2 hour. Theresulting slurry is then dried under a purge of dry inert gas such asnitrogen or argon, at atmospheric pressure and at a temperature of65±10° C. to remove the hydrocarbon diluent. The resulting compositionis in the form of a partially activated spray-dried precursor.

When additional activator compound is fed to the polymerization reactorfor the purpose of completing the activation of a partially activatedprecursor composition, or to activate completely, in one step, aninactivated precursor composition, it is fed into the reactor as adilute solution in a hydrocarbon solvent such as isopentane. Thesedilute solutions contain about 2 to 30% by weight of the activatorcompound.

The activator compound is added to the polymerization reactor so as tomaintain the Al/Ti ratio in the reactor at a level of about 10 to 500and preferably of 10 to 200.

EXAMPLES 1 TO 9

Ethylene was homopolymerized (in Examples 2, 8 and 9) and copolymerizedwith butene-1 (in Examples 1 and 3 to 7) in this series of Examples withcatalyst formed as described above and activated according to bothProcedure A (Examples 1 to 3 and 5 to 7) and Procedure B (Examples 4, 8and 9) to produce polymers having a density of >0.920 to ≦0.970.

Each of the polymerization reactions was continuously conducted for >1hour after equilibrium was reached and under a temperature as indicatedin Table I, a pressure of 300 psia and a gas velocity of about 3 to 6times G_(mf) in a fluid bed reactor system at a space time yield ofabout 3 to 7 lbs/hr/ft³ of bed space. The reactor system was asdescribed in the drawing, above. It had a lower section 10 feet high and131/2 inches in (inner) diameter, and an upper section which was 16 feethigh and 231/2 inches in (inner) diameter.

Table I below lists, with respect to Examples 1 to 9, various operatingconditions employed in such examples, i.e., the weight % of [MgCl₂ ]₂.5[TiCl₄ ][THF]₇ ; the type and amount of filler; Al/Ti ratio in thepartially activated precursor composition; polymerization temperature;H₂ /C₂ mol ratio; comonomer C₄ /C₂ mol ratio in reactor and catalystproductivity in terms of pounds of polymer produced/pounds of titaniummetal, reported in ppm of titanium metal. Table II below listsproperties of the granular virgin resins made in Examples 1 to 9, i.e.,density; melt index (MI); melt flow ratio (MFR); bulk density, averageparticle size, and content (percent by weight) of very small particles(<74 microns).

                                      TABLE I                                     __________________________________________________________________________    Reaction Conditions for Examples 1 to 9                                                         Filler                                Catalyst                   [MgCl.sub.2 ].sub.2.5 [TiCl.sub.4 ][THF].sub.7.0                                                   Amount                                                                             Al/Ti ratio in                                                                          Temp.                                                                             H.sub.2 /C.sub.2                                                                   C.sub.4 /C.sub.2                                                                    Productivity          Example                                                                            (wt percent) Type    (Wt. %)                                                                            part. act. precursor                                                                    °C.                                                                        mol ratio                                                                          mol ratio                                                                           (ppm                  __________________________________________________________________________                                                            Ti)                                       fumed silica                                                                        53                                                  1    16                        0         85  0.200                                                                              0.311 7.1                                       MgCl.sub.2                                                                          31                                                                      fumed silica                                                                        41                                                  2    27                        0         95  0.508                                                                              --    10.9                                      MgCl.sub.2                                                                          32                                                                      fumed silica                                                                        41                                                  3    27                        0         85  0.211                                                                              0.301 5.5                                       MgCl.sub.2                                                                          32                                                                      fumed silica                                                                        41                                                  4    27                        10        85  0.198                                                                              0.302 5.1                                       MgCl.sub.2                                                                          32                                                                      Al.sub.2 O.sub.3                                                                    40                                                  5    35                        0         85  0.209                                                                              0.310 3.3                                       Polystrene                                                                          25                                                                      fumed silica                                                                        40                                                  6    42                        0         85  0.207                                                                              0.300 6.1                                       Polystrene                                                                          18                                                  7    100            --    --   0         85  0.210                                                                              0.430 25.0                  8    90             fumed silica                                                                        10   6         95  0.513                                                                              --    18                    9    90             fumed silica                                                                        10   6         95  0.206                                                                              --    9                     __________________________________________________________________________

                                      TABLE II                                    __________________________________________________________________________    Properties of Polymers made in Examples 1 to 9                                                 Bulk    Aver. Part. Size of Spherical                                                               Very small particles                   Example                                                                            Density                                                                            M.I.                                                                             MFR Density, lbs/ft                                                                       Polymer Particles, microns                                                                  <74 microns, percent                   __________________________________________________________________________    1    0.926                                                                              2.3                                                                              28  21.9    630           0.6                                    2    0.970                                                                              4.8                                                                              28  28.1    418           4.7                                    3    0.924                                                                              2.5                                                                              27  18.0    757           0.4                                    4    0.922                                                                              2.3                                                                              26  21.8    1008          0.6                                    5    0.927                                                                              3.5                                                                              26  18.1    848           0.0                                    6    0.930                                                                              2.7                                                                              26  21.2    554           0.4                                    7    0.927                                                                              1.0                                                                              24  15.0    737           --                                     8    0.969                                                                              6.4                                                                              28  28.1    787           <2.0                                   9    0.959                                                                              1.1                                                                              28  25.6    863           <2.0                                   __________________________________________________________________________

The data of Table II show that when a precursor composition is spraydried without containing filler (Example 7) the bulk density is low.Also the polymer particles formed in Example 7 were a fibrous mass witha cotton-like consistency.

What is claimed is:
 1. A catalyst composition produced by(A) forming a spherical precursor composition of the formula:

    Mg.sub.m Ti.sub.1 (OR).sub.n X.sub.p [ED].sub.q [Filler].sub.r

wherein R is a C₁ to C₁₄ aliphatic or aromatic hydrocarbon radical, or COR' wherein R' is a C₁ to C₁₄ aliphatic or aromatic hydrocarbon radical, X is Cl, Br, I, or mixtures thereof, ED is an electron donor compound, Filler is an inert filler compound, and, based on the total weight of said composition, m is ≧0.5 to ≦56, n is 0 or 1, p is ≧2 to ≦116, q is ≧2 to ≦85, and r has a value such that the percent filler is from about 10 to about 95 weight percent based on the total weight of said composition, by forming a slurry or solution of at least one magnesium compound and at least one titanium compound and at least one filler compound in at least one electron donor compound so as to thereby form a slurry or solution of said precursor composition in said electron donor compound and spray drying said slurry or solution by atomization to form spherical particles of said precursor composition which have a particle size of from about 10 to about 200 microns, said magnesium compound having the structure MgX₂, said titanium compound having the structure Ti(OR)_(a) X_(b) wherein a is 0, 1 or 2, b is 1 to 4 inclusive and a+b=3 or 4, said electron donor compound being a liquid organic compound in which said magnesium compound and said titanium compound are soluble and which is selected from the group consisting of alkyl esters of aliphatic and aromatic carboxylic acids, aliphatic ethers, cyclic ethers and aliphatic ketones, and (B) activating said precursor composition either by partially activating it with >0 to ≦10 moles of activator compound per mol of Ti in said precursor composition, or completely activating it with 10 to 500 mols of activator compound per mol of Ti in said precursor composition, said activator compound having the formula

    Al(R").sub.c X'.sub.d H.sub.e

wherein X' is Cl or OR'", R" and R"' are the same or different, and are C₁ to C₁₄ saturated hydrocarbon radicals, d is 0 to 1.5, e is 1 or 0 and c+d+e=3, said activating being conducted after the recovery of said particles of said precursor composition by treating the precursor composition with said activator compound.
 2. A composition as in claim 1 in which said magnesium compound comprises MgCl₂.
 3. A composition as in claim 2 in which said electron donor compound comprises at least one ether.
 4. A composition as in claim 3 in which said electron donor compound comprises tetrahydrofuran.
 5. A composition as in claim 4 in which said titanium compound comprises TiCl₄. 